In the wake of the successes in molecular biology, revealing information packed in the genome, behavioral scientists face the daunting task of integrating molecular events into the context of the whole organism, a challenge intensified by growing awareness that the behavior of one individual is exquisitely sensitive to the behaviors of others. Thus to understand the chain of events by which molecular events affect behavior we must not only place those events in the context of a single individual, but also in the context of individuals interacting with one another. Including this social sphere into our understanding will be crucial if we are ever to understand human behavioral disorders, since the most common of these (depression, schizophrenia, drug abuse) are very sensitive to the social environment. We propose interdisciplinary training of investigators to consider behavior from multiple levels of analysis, from molecular and cellular events to behavioral outcomes in a social context. Because social interactions can be tremendously complex, we must select models in both traditional and non-traditional species to take advantage of those specific influences of one individual upon the brain and behavior of another. As examples, we study: social learning of song in zebra finches; maternal stimulation of neonates in rats, mice, and voles; dominance hierarchies in spotted hyenas; social modulation of puberty in rats, Syrian hamsters and Siberian hamsters; as well as mating behaviors in a variety of vertebrates. Most of these models also reflect the influence of hormones upon neural structure and behavior because hormones mediate many social signals, and because hormones affect myriad targets in the body, including the brain, to coordinate behavior. These hormone-sensitive systems permit us to study molecular events, too: secretion of specific hormones, activation of hormone receptor proteins, hormonal modulation of gene expression in the nervous system, nuclear co-factor proteins regulating hormone responsiveness, environmental contaminants altering reproductive behavior, brain peptides regulating parental behaviors, among others. This integration of information, from molecular to social events and back again, must be accomplished for any satisfying understanding of behavior. We have assembled a unique program to train the next generation of researchers to tackle the challenge of studying the contextual determinants of behavior.